A radio is a device that wirelessly transmits or receives signals in the radio frequency (RF) part of the electromagnetic spectrum to facilitate the transfer of information. Today, radios exist in a multitude of items such as cell phones, computers, car door openers, vehicles, and televisions.
Traditional hardware based radios limit cross-functionality and can only be modified through physical intervention. This results in higher production costs and minimal flexibility in supporting multiple wireless communication standards. By contrast, software defined radio (SDR) technology provides an efficient and comparatively inexpensive solution to this problem, allowing multi-mode, multi-band and/or multi-functional radios that can be enhanced using software upgrades.
SDR defines a collection of hardware and software technologies where some or all of the radio's operating functions (also referred to as physical layer (PHY) processing) are implemented through modifiable software or firmware operating on programmable processing technologies. These devices include field programmable gate arrays (FPGA), digital signal processors (DSP), general purpose processors (GPP), programmable System on Chip (SoC) or other application specific programmable processors. The use of these technologies allows new wireless features and capabilities to be added to existing radio systems without requiring new hardware.
Thus, a SDR is a radio whose components, which in a hardware-based radio would have been implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.), are instead implemented by means of software on a personal computer or embedded computing devices. Software defined radios find use in the afore-mentioned personal computer and a number of other portable devices. A basic SDR may include a personal computer equipped with analog-to-digital converter, preceded by a radio frequency (RF) frontend. Significant amounts of signal processing are handled by a programmed general-purpose processor, rather than being done in special-purpose hardware. Such a design produces a radio that can receive and transmit widely different wireless communication protocols based solely on the software used.